Might my [21M] girlfriend [22F] be cheating on me or I’m just overthinking?

Anyone who has the time please read this, I’m desperate for help…

TL;DR: I suspect my girlfriend might be having a long distance relationship because of photos that I found on her Google Photos (nothing completely “incriminating”) and other stuff that has changed after a trip she took to Mexico, specially that she says that if I leave her it’s ok and the fact that she doesn’t talk to her friends no more unless I’m not home… she wants to go to back to Mexico soon too

Well, I have to mention that we’ve been 4 years together and I’ve never been the jealous type and much less a toxic guy and anyone could tell you that. We live in the US and she has no family or friends here (she was born here so she doesn’t want me for green card and much less money cause I don’t have any).

Thing is, I have her Gmail because I manage all her credit cards there and track shippings of the things that we order cause she doesn’t know how and prefers that I do it, anyway, yesterday morning I forgot to switch back to my account after reading a credit card statement and later at night time I decided to check my Google Photos for the nostalgia yk, and since I didn’t switch in the morning I got logged in to her Photos account and as I was about to switch to my account, I saw some of those pictures that you’d send to your bf/gf, you know, those cute anime/Sanrio/animals pictures with things written on it like “for the best person I know” “have a beautiful day just like you” etc. and I have to admit I did get curious and weirded out cause last time she sent me one of those pictures was probably 2-3 months ago, so I kept scrolling down, just to see tons of pictures like that that she never sent me, and well, I didn’t think much of it until I saw a ton of photos of one of her male friends, a good amount of them were random screenphotos from a video call and photos of his ID, when he was a kid, etc. and that amount of photos and the randomness of them (especially that one kid pic and the video call) instantly reminded me of when we just started our relationship cause we wanted all the photos of each other that we could get. Again, I tried to remain calm and didn’t think much of it until I saw a screenshot of some messages that he sent to her saying “It’s just that; I only want you; I don’t need anything else; if not I’ll share it with you”, that one last message didn’t make much sense to me since I didn’t know the context of their conversation and what was he referring to.

Anyway, as much as I tried not thinking anything of it, I instantly started to make connections of all things that been going on, first of all, that guy that I’m referring to lives in Mexico, she went by herself to Mexico on March this year to get a surgery and came back on May, a couple little things changed after she returned. Second of all, I have to mention that all the screenshots and images that I found are from August and onwards, so if anything, this started 2 months after (i think) she came from Mexico, anyway, after that, she started telling me that if I ever stop loving her and want to leave her she would understand and that she would prefer it over me cheating on her or hating her on secret, she told me things about leaving her a couple times for like 2 months.
I never thought about this because ever since she came back she’s been the same sweet girl that I know, so this really has me thinking. More things to consider is that after she came back, she played a lot online with her friends from Mexico and talk over the mic for hours which was normal, that was on July-August, but these last months, she doesn’t make voice calls anymore and doesn’t play with all of her friends, she plays mainly with that one friend and if I’m there, they never talk over the mic “cause she doesn’t feel comfortable talking while I’m there” (how curious that she didn’t mind that before tho), and when I work, she constantly asks me if I’m going to hang out with my friends that day to know if I’ll be coming home after work or later, in few words, she only talks with him if I’m not there ???.

One last thing but I think REALLY important, and this is NSFW so, just letting you know, when she was in Mexico the same thing with the Google Photos happened and guess what I found? I found photos of her b**bs that again, she never send to me, I did call her out on this that day and she only told me that they were for me but she got shy and didn’t send them, I believed it back then and didn’t mention anything afterwards, tho I did think that last time she send me nudes was more than a year ago. And then, before she went to Mexico, we used to have a lot of An*l sex and I always asked her if that was something she liked and she said yes, but after she came back, she’s never want to do it ever again, which I don’t mind, if she doesn’t like it then we don’t do it, but now I’m suspecting of everything and why everything happened after that trip…

What should I do guys? If she is having a long distance relationship then that’s something I can’t forgive and I’ll have to break things up, but I’m not ready to do so… thing is, I have to do something today cause last night I did not sleep a thing because of this and I can’t stop shivering right now, I have to talk about this ASAP, but I know she’ll just deny everything I say if I say it straight and she can even flip the situation and say that I’m toxic or something because I miss interpreted things and I don’t have evidence (cause that’s true, I don’t have any direct evidence of them confessing their feelings, just a bunch a love images, a couple non totally incriminating screenshots and photos of the guy).

Dude, she’s the most wonderful person I’ve met and we literally have the same taste on everything, this sucks cause it’s been 4 years and I love her so much, and to find someone like her on the future, that’s going to be difficult…

Oh and she did mention that she’d love to go back to Mexico to see her friends and family asap.

P.D. Some of those love pics mentioned distance and well, we’ve been living together for 2 and half years…